Thesis
Interactions of grid-forming converters for windfarm applications
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2023
- Thesis identifier
- T16602
- Person Identifier (Local)
- 201986378
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- The electricity network is undergoing a paradigm shift due to the strive for cleaner generation and enhanced electrification of heat, transport and industry. Due to the removal of synchronous generation and the increased penetration of inverter-based resources numerous issues have been highlighted. The reduction of system inertia, frequency response, lower fault current provision and apparent decline in system strength are all leading to reduced frequency, voltage and harmonic stability on the network. To remedy this, converters are being designed with enhanced grid services to replicate the useful behaviour lost with the removal of synchronous generation. Conventional grid-following structures are being augmented with enhanced power and voltage control loops and grid-forming converters have been suggested as a promising source of inertia, frequency response and system strength. However, with the inclusion of these structures the way the network interacts is fundamentally changing and new analysis techniques are required to properly represent the system. The structures are capable of deployment into any inverter-based resource however this work takes a main focus on wind energy which is the fastest growing renewable energy source at present with a high volume of capacity already installed. Additionally, wind farms are often located far from shore leading to long transmission lines, high impedances and weak networks. This makes them an ideal case for testing the interactions of grid following and forming converters. This thesis explores different methods of analysing the interactions in wind parks via the system impedances. The mathematical implications of the system admittance when including converter control action are explored. This analysis is used to justify the use of multiple-input multiple-output models for study over simpler Single-Input Single-Output models. The interactions between single and multiple turbine systems are then explored using impedance-based stability techniques where a new method of analysing the system is proposed capable of dealing with issues of previous techniques and allowing the system to be studied from different points of view. The interactions of different grid-following and grid-forming structures are explored with the robustness of each combination explored. Following this the link between system strength and stability is explored where a novel method of determining system strength is proposed (known as GSIM) incorporating converter control action and decoupling system strength from fault current provision. This method is used to investigate the useful or detrimental behaviour of each control topology towards system strength. Finally, all analyses are combined to analyse a full wind farm including multiple turbines capable of operating under different control structures. This allows the work to answer the important question, what is the appropriate balance of grid forming to grid following in a wind park and what system components affect this. Moreover, the optimal location to place grid-forming turbines is explored in terms of providing system strength and stability.
- Advisor / supervisor
- Alvarez, Agusti Egea
- Holliday, Derrick
- Xu, Lie
- Resource Type
- DOI
Relazioni
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PDF of thesis T16602 | 2023-06-07 | Pubblico | Scaricare |